1. Field of the Invention
This invention relates in general to the manufacture and structure of magnetic heads, and more particularly to a method for forming a coil with higher copper density in the magnetic head using a process combining damascene and non-damascene processes.
2. Description of the Prior Art
In the last decades, magnetic hard drives (or disc drives) have been in common use for storage of large groups of data. Improvements in manufacturing thereof have attracted popular attention particularly to reducing the size of the drive and/or its internal components to achieve both lower costs and wider applications.
Magnetic hard drives include magnetic recording head for reading and writing of data. As well known, a magnetic recording head generally includes two portions, a write head portion or head for writing or programming magnetically-encoded information on a magnetic media or disc and a reader portion for reading or retrieving the stored information from the media.
Data is written onto a disc by a write head that includes a magnetic yoke having a coil passing there through. When current flows through the coil, a magnetic flux is induced in the yoke, which causes a magnetic field to fringe out at a write gap in a pole tip region. It is this magnetic field that writes data, in the form of magnetic transitions, onto the disk. Currently, such heads are thin film magnetic heads, constructed using material deposition techniques such as sputtering and electroplating, along with photolithographic techniques, and wet and dry etching techniques.
Examples of such thin film heads include a first magnetic pole, formed of a material such as NiFe which might be plated onto a substrate after sputter depositing an electrically conductive seed layer. Opposite the pole tip region, at a back end of the magnetic pole, a magnetic back gap can be formed. A back gap is the term generally used to describe a magnetic structure that magnetically connects first and second poles to form a completed magnetic yoke.
One or more electrically conductive coils can be formed over the first pole, between the pedestal and the back gap and can be electrically isolated from the pole and yoke by an insulation layer (or insulator spacers or insulators), which could be alumina (Al2O3) or hard baked photoresist.
In operation, the disk (or disc) rotates on a spindle controlled by a drive motor and the magnetic read/write head is attached to a slider supported above the disk by an actuator arm. When the disk rotates at high speed a cushion of moving air is formed lifting the air bearing surface (ABS) of the magnetic read/write head above the surface of the disk.
As disk drive technology progresses, more data is compressed into smaller areas. Increasing data density is dependent upon read/write heads fabricated with smaller geometries capable of magnetizing or sensing the magnetization of correspondingly smaller areas on the magnetic disk. The advance in magnetic head technology has led to heads fabricated using processes similar to those used in the manufacture of semiconductor devices.
The read portion of the head is typically formed using a magnetoresistive (MR) element. This element is a layered structure with one or more layers of material exhibiting the magnetoresistive effect. The resistance of a magnetoresistive element changes when the element is in the presence of a magnetic field. Data bits are stored on the disk as small, magnetized region on the disk. As the disk passes by beneath the surface of the magnetoresistive material in the read head, the resistance of the material changes and this change is sensed by the disk drive control circuitry.
The write portion of a read/write head is typically fabricated using a coil embedded in an insulator between a top and bottom magnetic layer. The magnetic layers are arranged as a magnetic circuit, with pole tips forming a magnetic gap at the air bearing surface (ABS) of the head. When a data bit is to be written to the disk, the disk drive circuitry sends current through the coil creating a magnetic flux. The magnetic layers provide a path for the flux and a magnetic field generated at the pole tips magnetizes a small portion of the magnetic disk, thereby storing a data bit on the disk.
Stated differently, data is written onto a disk by a write head that includes a magnetic yoke having a coil passing therethrough. When current flows through the coil, a magnetic flux is induced in the yoke, which causes a magnetic field to fringe out at a write gap in a pole tip region. It is this magnetic field that writes data or data bits, in the form of magnetic transitions, onto the disk. Such heads are typically thin film magnetic heads, constructed using material deposition techniques such as sputtering and electroplating, along with photolithographic techniques and wet and dry etching techniques.
The read/write head is formed by deposition of magnetic, insulating and conductive layers using a variety of techniques. Fabrication of the write head coil requires a metallization step wherein the metallization is formed in the shape of a coil. The damascene process is one of the techniques used for forming metallization layers in integrated circuits. Generally, the damascene process involves forming grooves or trenches in a material, and then electroplating to fill the trenches with metal. After a trench is formed, however, a seed layer must first be deposited in the trench to provide an electrically conductive path for the ensuing electrodeposition process. Metal is then deposited over the entire area so that the trench is completely filled.
The damascene process used in semiconductor device fabrication requires fewer process steps compared to other metallization technologies. To achieve optimum adherence of the conductor to the sides of the trench, the seed layer deposited prior to deposition of the metal must be continuous and essentially uniform.
The increasing demand for higher data rate has correspondingly fueled the reduction of the yoke length, coil pitch and hence the overall head structure. This allows for higher speeds (rpm) disk drives having high performance. In addition to a compact design of the yoke (shorter yoke), low coil resistance is desirable for which damascene techniques are used to form a thick coil in a compact area. Additionally, more copper or coil is desirable to reduce coil resistance, which reduces write-induced protrusion. Write-induced protrusion occurs during writing to the disk because when temperature increases as a result of hotter coils, it causes the write head to expand and come in contact with the disk. Any such contact with the disk is clearly highly undesirable because of the damage caused to the disk. Thus, there is a need to decrease coil resistance.
In damascene techniques, hard baked photoresist is used as a medium, onto which coil is formed. However, fairly large spaces are present in between coil turns in current coil manufacturing techniques. The spaces are typically filled with baked photoresist and are basically thick insulator walls. For example, a typical thickness of the insulator wall is 300 nanometers. Since coil resistance for Damascene coils is determined by how thick the insulator walls are and how tall the coil turns are, thick insulator wall reduces copper density and causes higher coil resistance.
Briefly, in current manufacturing techniques, the photoresist material is baked and exposed to create holes and then when copper is plated in the holes to form coil(s) thereupon. The photoresist material is then either removed or left in. Damascene techniques allow for higher aspect ratio and therefore lower resistance, nevertheless, in current techniques, the fairly large spaces between the coil turns prevent attaining even lower resistance. In non-damascene techniques, the seed layer is deposited prior to the photoresist material but higher aspect ratios are again unattainable due to the presence of thick insulator walls.
Another advantage of reducing spaces that are other than copper is to lower write head expansion at an elevated temperature. That is, photoresist having a large coefficient of thermal expansion benefits from reduced volume because temperature-induced protrusion is then reduced.
By way of brief background, in FIG. 1, relevant portions of a prior art disk drive 10 is shown to include a photoresist 14 onto which a coil 12 is formed having a center tap 16. A P1 pedestal layer 20 is shown formed below the bottom of the photoresist 14 at the ABS 18. A back gap layer 22 is shown below the center tap 16 surrounded by the coil 12. In fact, the coil 12 is formed between the P1 pedestal layer 20 and the back gap layer 22 forming a yoke.
It is desirable to decrease the photoresist 14 and increase the coil 12 for the foregoing reasons, among others. In FIG. 2, a cross sectional view, at AA, of the disk drive 10 of FIG. 1, is shown at 90. Coil turns 86 form the coil 12 of FIG. 1 and the insulators (or spaces) 88 shown between the coil turns 86 form the photoresist 14 of FIG. 1. A first pole P1 is shown on top of which is disposed the back gap layer 22, the coil turns 86, which are relatively small in size, and the insulators 88, which are relatively large in size therefore causing disk drive performance issues, such as write-induced and temperature protrusion.
Thus, there is a need for forming a coil having more copper and less insulation space between coil turns in a compact area of a magnetic head using damascene and non-damascene processes.